Electromagnetic relay



Patented June 26, 1934 UNITED STATES PATENT OFFICE Bell TelephoneLaboratories New York, N. Y., a corporation Incorporated, I l of NewYork Application February 27, 1932, Serial No. 595,521

3 Claims.

This invention relates to electro-magnetic relays and particularly tovibrating relays for use in high speed telegraph repeaters.

An object of the invention is to make it possible 5' to convenientlyadjust the relay for operation at different frequencies within a widerange without impairment of its efiiciency.

Relays of this type are used in systems in which the signals arecomposed of positive and negative impulses as well as in systems inwhich the signals comprise periods of openings and closures of the linecircuit. The relay is provided with operating windings connected in oneline circuit and an armature with contacts responsive to impulsesthrough the operating windings to impress corresponding impulses upon asecond line circuit. In the case of the first type of system, referredto above, the operating windings are effective in operating the armatureto one side in response to 20' a plus impulse and to the other side inresponse to a minus impulse; in the case of the other type of system animpulse through the operating wind-' ings will operate the relay to oneside overcoming biasing means which, in the absence of an impulse,operate the armature to the other side. For examples of both of thesetypes of systems with the corresponding two types of relays referencemay be had to the disclosure in my Patent 1,701,- 100 issued on February5, 1929.

The vibrating type of relay is provided with an accelerating Windingwhich is included in a vibrating circuit made self-interrupting by beingconnected through the armature and its contacts to suitable sources ofpotential, which ordinarily also supply the current impulses to thesecond line circuit referred to above.

The invention is particularly adaptable to a vibrating relay of thetype, such as is shown in my Patent No. 1,701,100, issued February 5,1929. In accordance with the arrangement shown in that patent thevibrating circuit besides the accelerating winding includes a condenserand a transformer having primary and secondary windings. In the absenceof current in its operating windings the relay would vibrate at afrequency determined by the constants of the vibrating circuit. In thepresence of impulses through the operating winding, the vibratingcircuit, as is well known, aids in the quick and reliable operation ofthe armature, when the relay is operated at a signaling frequencyapproximately equal to or below the periodicity of the vibratingcircuit.

It would be convenient to supply vibrating relays of this type in astandard form for use in telegraph systems operating at differentfrequencies, such systems in accordance with standard practice workingat frequencies of twenty-seven cycles per second or at thirty-six cyclesper second. A limited variation in the periodicity of the vibratingcircuit may be obtained by varying the condenser, which however wouldhave the disadvantage of distorting undesirably the current in theaccelerating winding and therefore to impair the efficiency of thecircuit.

In accordance with the invention means are provided for readilyadjusting the characteristics of the vibrating circuit for operation atdifferent frequencies within a wide range. The fre- 2'0 3 quency controlmeans are adapted to reduce the inductance included in the vibratingcircuit and in the preferred forms comprise a by-pass for at least aportion of the transformer windings N and switching means for changingthe by-pass and thereby changing the effective inductance of thetransformer and correspondingly changing the frequency of the vibratingcircuit. By providing a resistance by-pass for a portion of the primarywinding of the transformer which may be opened or closed by means of amanually operated key, a wide change in frequencies may be obtainedwithout the disadvantage of distortion" referred to above. H

In the following description of the details and operation of theinvention as exemplified by a preferred form, reference will be made tothe attached drawing in which:

Fig. l is a diagrammatic representation of a telegraph repeater stationof a conventional type employing a vibrating relay in accordance withthe invention; and

Fig. 2 is a curve showing the relation between the resistance by-passand the periodicity of the relay when used with a particulartransformer.

Referring first to Fig. 1, the vibrating relay R is of the polarizedtype having line windings 20 and 21- and accelerating winding 22 for theoperation of armature 23 between the marking contact m and the spacingcontact s connected respectively to negative and positive sources ofpoten-- tial. The line windings 20 and 21 are connected in a well knownmanner into a differential duplex system comprising a line circuit 30connected to an impulse transmitting device 31 and a line L running to adistant station, with equipment similar to that of the station shown inthe drawing. The transmitter 31 may be located at the same station asthe relay R or may be at a re- 1'16 mote station and it may be of anyconvenient design for impressing positive and negative impulses upon theoperating windings of relay R in accordance with a telegraph code.

When no signals are being transmitted, transmitter 31 and the distanttransmitter both apply a negative potential to the line, so that no linecurrent flows in winding 20; current in the local circuit throughwinding 21 holds the armature in marking position. When transmitter 31is operated to apply positive potential to the line, the local currentthrough winding 21 reverses but the line current through winding 20being of double the strength of the local current still holds thearmature in its marking position; the relay thus is not operated byoutgoing signals from transmitter 31. With the distant transmitterapplying positive potential to the line the relay will remain in spacingposition since, when transmitter 31 applies positive potential to theline, the line winding 20 would be without current and winding 21 wouldmove the armature to spacing, and when transmitter 31 applies negativepoten tial to the line the winding 21 would receive reversed current butwould be overpowered by the line winding receiving current of double thestrength of the local current to hold the armature in spacing position.A receiving device 32, which may be a polarized sounder or a recordingdevice located at this station or at a remote station, is connected overthe line circuit 33 to the armature 23 and thus will receive positive ornegative impulses in accordance with similar impulses received over theline L.

The accelerating winding 22 is connected into a vibrating circuit, aportion of which comprises a closed circuit through condenser C,secondary winding SW and primary winding PW, in series, of transformerT, accelerating winding 22 and low resistance LR. At the point P asupply circuit is connected to this closed circuit over high resistanceHR, armature 23 and contacts m or s to negative or positive sources ofpotential respectively. The connecting point between the primary andsecondary winding is grounded to provide a return path to the negativeand positive sources at contacts m and s.

Assuming the condition shown in the drawing according to which thearmature 23 is held against the marking contact by a negative potentialapplied to the line at the distant station, negative potential issupplied to the vibrating circuit over high resistance HR, condenser C,secondary winding SW to ground, thereby maintaining a charge upon thecondenser C; another circuit may be tracedfrom the point P over lowresistance LR, accelerating winding 22, primary winding PW to ground.The accelerating winding under this condition opposes the operatingwindings and tends to move the armature toward the spacing contact witha force which, however, is not sufficient to overcome the force of theoperating windings.

Assuming now that a positive impulse arrives over the line L through thewinding 20, the armature 23 will move away from the marking contact andthe negative potential will be removed from the vibrating circuit. Theenergy stored in transformer T and condenser C discharges through theaccelerating winding 22 which continues to act on the armature in thedirection toward the spacing contact, thus aiding the line windings inthis operation. When the armature reaches the spacing contact, all threewindings act to place the armature firmly against the contact for ashort interval. A positive potential is now applied over the highresistance to point P and the condenser C will be charged in theopposite direction of its previous charge and the transformer Tsimilarly stores energy in the reverse direction of the previouslystored energy over the circuit through low resistance LR, acceleratingwinding 22 and primary winding PW. The current through acceleratingwinding 22 thus having been reversed, this winding tends to move thearmature towards the marking contact in opposition to the operatingwindings and the whole circuit now is in condition for repeating theoperations just described in the opposite direction when a negativeimpulse arrives over the line L.

For given mechanical dimensions of the relay the periodicity of thevibrating circuit is mainly determined by the inductance of thetransformer windings and the accelerating winding and by the capacity ofcondenser C, and this natural periodicity of the circuits adapts therelay for most efficient operation at signaling frequencies deviatingbut slightly therefrom.

In order that a relay circuit of this type may readily be used with highefficiency under different circumstances and particularly in systemshaving different signaling frequencies or in sys-- tems in which thefrequency is changed for certain periods of the day, provision is madefor readily adjusting the periodicity of the vibrating circuitforoperation at different frequencies. For this purpose an adjustableresistance 40 is bridged across a portion of the primary winding oftransformer T and a key 41 serves to connect or disconnect this by-passfrom the transformer winding. By means of this resistance by-pass acertain fraction of the current through the accelerating winding isdiverted from a portion of the primary winding, thereby changing themutual inductance between the transformer windings and consequentlyreducing the natural periodicity of the relay.

In general telegraph practice frequencies of twenty-seven andthirty-five cycles per second are frequently used. The relay with itsassociated transformer and condenser may be designed to operate attwenty-seven cycles per second when the key 41 is left open, and theresistance 40 may be adjusted to change'the frequency of the vibratingcircuit to thirty-five cycles when the key 41 is closed. In this mannerthe relay circuit may readily be used universally in both types ofsystems.

For the sake of illustrating the effect of the resistance by-pass uponthe frequency of the relay, observations taken from experiments with agiven relay are shown in Fig. 2, in which the curve represents therelation between the resistance values of resistance 40 and thecorresponding periodicities of the relay. This curve shows that with aresistance of 1000 ohms a frequency of about thirty-five cycles would beobtained, and that the frequency of about twenty-five or twentysixcycles is approached as the resistance is increased to infinity. Thecurve further shows that by still further reducing the resistance of thebypass the frequency may be increased considerably.

It is, of course, possible to attain the desired result by differentarrangements of by-pass and transformer windings which readily wouldsuggest themselves to those skilledin the art. Thus the resistanceby-pass may bridge any fraction of the primary winding or the totalwinding, and different taps may be taken between resistance andtransformer windings with switching means in each tap for obtaining aplurality of periodicities; the principal object being to reduce theinductance of the transformer circuit, the resistance Icy-pass may beconnected at other points of the transformer to serve this purpose, suchas between points on the primary and secondary windings. 7

As has been stated above the invention is applicable to relays used insystems in which the signals comprise current and no-current impulses;in this case only one line winding would be used and a biasing windingmay be provided for reversing the operation of the armature duringno-current intervals in the line winding; this well known arrangement isdescribed and illustrated in my Patent 1,701,100. The ampere turns ofthe biasing winding would ordinarily be about one-half the ampere turnsof the line winding and the ampere turns of the accelerating windingwould be still less than those of the biasing winding in order to insurethat the relay will not operate when the accelerating winding is opposedto the biasing winding. In all other respects the arrangement and itsoperation would be similar to the arrangement described above.

What is claimed is:

1. An electrical relay comprising an armature for eifecting circuitchanges, an operating winding to operate said armature, acceleratingmeans to control the operating speed of said relay including a windingfor aiding and opposing said operating winding in the operation of saidarmature and also including circuit means having capacity andinductance, and means for changing the operating speed including aby-pass for at least a portion of said inductance and switching meansfor said by-pass.

2. A polarized electrical relay for operation at Ya plurality ofsignaling frequencies comprising an armature for efiecting quick circuitchanges, an operating winding to operate said armature in response tosignal impulses through said winding, an accelerating winding to aidsaid operating winding in operating said armature, a vibrating circuitfor said accelerating winding including a condenser and a transformerhaving a winding, a source of current for said circuit adapted to beinterrupted from said circuit by the movements of said armature, aresistance by-pass for atleast part of said transformer winding, andmeans for varying the resistance of said by-pass to vary the periodicityof said vibrating circuit.

3. In a telegraph repeater, a vibratingrelay having operating andaccelerating windings and an armature for effecting changes in anoutgoing circuit in accordance with signals received by said operatingwinding, an accelerating circuit for said accelerating winding includingsaid armature, a condenser and a transformer having primary andsecondary windings, a resistance bypass for at least a portion of saidprimary winding, and contact means for opening and closing said by-passto change the periodicity of said relay from one value to anothersubstantially different value.

GEORGE C. CUMMINGS.

